function go6(){ 
    let c = document.getElementById('lesson6')
    let ctx = c.getContext('2d') 
    var video =document.querySelector("#video-ls6");
    // 获取按钮
    let btn = document.querySelector("#btn-ls6");
    btn.onclick =function(){
        if(video.paused){
            video.play();
            render()
        }else{
            video.pause()
        }
    }
    
    var img = new Image();
    img.src ="./imgs/dama.png";
    function render(){
        ctx.drawImage(video,0,0,400,220);
        ctx.drawImage(img,150,50,100,50);
        requestAnimationFrame(render);
    }
} 